Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/1/2011
Publication Date: 9/13/2011
Citation: Li, P., Chen, J., Wu, P., Zhang, J., Chu, C., See, D.R., Brown Guedira, G.L., Zemetra, R., Souza, E.J. 2011. Quantitative trait loci analysis for the effect of Rht-B1b dwarfing gene on coleoptile length and seedling root length and number of bread wheat. Crop Science. 51:2561-2568 (2011). Interpretive Summary: The gene responsible for height in wheat was investigated for its additional role in other plant development processes. Besides height gene effects on coleoptiles length, it was determined that the plant height genes also impcat the development of root biomass and root numbers.
Technical Abstract: It has been documented that the dwarfing genes, Rht-B1b and Rht-D1b, can reduce wheat (Triticum aestivum L.) coleoptile length (CL), but their effect on number of roots (RN) and root length (RL) have not been determined. Our objectives were to identify quantitative trait loci (QTL) controlling CL, RN, and RL and to determine if any of the QTL correspond to wheat dwarfing genes. A population consisting of 159 recombinant inbred lines (RILs) was derived from the cross of Rio Blanco (Rht-B1b, Rht-D1a), a semidwarf cultivar with short CL, and IDO444 (Rht-B1b, Rht-D1a), a tall germplasm with long CL. The CL, RN, longest root length (LRL), and total root length (TRL) were evaluated at two temperature regimes (18 and 22'C). A major QTL mapped to the Rht-B1 locus on chromosome 4B explained 64% of the phenotypic variation for CL, 9% for LRL, 26% for TRL, and 14% for plant height. The CL of the semidwarf RILs was significantly less than that of the tall lines while the reverse results were observed for LRL and TRL. Our results indicated that the Rht-B1 gene had the pleiotropic effect of decreasing CL while increasing LRL and TRL. None of the six QTL for RN were mapped to the regions containing the Rht-B1 locus although semidwarf RILs had more roots than the tall lines. This study suggested that selection of the Rht-B1 allele tended to increase root biomass, perhaps ameliorating its negative effect of reduced CL.